Birmingham police today defended their decision to evacuate 20,000 people from the city centre last night insisting there had been a "real and significant" threat to lives.

West Midlands police held a press conference to explain their actions after reopening the city's ring road early this morning and lifting the cordon around the city's Broad Street entertainment district and Chinese quarter.

Last night, four controlled explosions were carried out on suspect packages on a bus in the city centre and packages were examined at a hotel.

Speaking from the force's headquarters, Chief Constable Paul Scott-Lee said the packages that prompted the evacuation were neither bombs nor hoax explosive devices, but stressed information received by officers had been significant enough to warrant the emergency procedure last night.

The city centre, full of revellers at the beginning of the evening, was left a ghost town as groups out celebrating hen nights and birthdays, along with workers, were evacuated to the perimeter of the centre from 8.40pm.

In the wake of Thursday's attacks on London, Mr Scott-Lee said, the emergency services had to respond after police received calls from members of the public concerned about discarded items.

He said: "Last night, we took the unusual step of evacuating parts of Birmingham city centre and asked members of the public to go home. I can tell you that, bearing in mind the current world climate, the information we received posed a real threat to the lives of people in the city centre."

The public's safety was the top priority, he said, adding: "I believe this threat was significant for me to authorise this evacuation. The packages were incidental to the threat we were responding to."

Asked if the evacuation was an over-reaction by police after last week's events in the capital, he said: "There was a significant threat. Alert members of the public saw things that gave them concern and they responded to it."

No attempts were made to make the packages look like bombs, said the police chief.

"We have found no bombs, but we have responded to what members of the public saw and thought was suspicious and which they quite responsibly drew to our attention," he said.

Despite last night claiming that the situation was unrelated to the London attacks, today Mr Scott-Lee admitted recent terrorist attacks did influence the decision to evacuate.

"When we are making any assessment of threat analysis, we have to make it in the context of what has happened in the immediate time frame," he said.

Police are appealing for the public to remain vigilant and not be put off by false alarms such as those in Birmingham. Anyone seeing an unaccompanied package in a public space should still raise the alarm.